Hey, just wanted to suggest a couple things.
Feminine Aspects suggestions:
I think it'd be awesome if you added sliders for breast firmness/droopiness, waist width, and hip width because having only the feminine/masculine and breast roundness sliders to affect these things really feels limiting.
However, the breast firmness slider would in nature be something that affects both shapekeys and physics, which may be an issue implimenting, at least according to what I know about Unreal.
Fat and Belly suggestions:
I also think that it would be nice to be able to change belly shape, in which case possibly floppy aprons of fat or big jelly rolls could be in order, or maybe just fat distribution, because it seems like the muscle/fat sliders don't do much other than change the shape of the body parts they affect.
Note:
I think that the body shape customization is very constricting personally, and as a person with ADHD, I highly value variety in games and I don't like having to manually edit the shape of my character by investing points strategically, often resulting in me either begrudgingly sacrificing points out of dedication or having to choose a different "class."
TL;DR- Well, if I felt that reading the whole thing wasn't important, I wouldn't have typed anything at all. I have titled each section for your convenience.
P.S. I wanted to note that everything could use more realistic physics, especially at smaller and larger sizes.